staging: wilc1000: fix "ERROR: do not initialise globals to 0 or NULL"

This patch fixes the checkpatch.pl error to host_interface.c.
 - ERROR: do not initialise globals to 0 or NULL

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>